Biochemistry

emergency mobilization of fatty acids from the fat depots. Consequently, the development of hyperlipemia contributes to the conservation of carbohydrates with their lack. The exceptions are the liver and brain, which do not use ketone bodies as a source of energetic material. In muscles and other tissues, acetone bodies oxidize to form ATP. 10.3 BIOSYNTHESIS OF FATS The ability of humans and animals to store glycogen is limited, so the amount of glucose entering the body may exceed its energy needs. At the same time, glucose is used as a “ building material ” for the synthesis of fatty acids and glycerol, which are converted into triacylglycerol, which is deposited in the “ fat depot ” . In the synthesis of triacylglycerols, three stages are conventionally distinguished: the formation of glycerol, the synthesis of fatty acids, the interaction of glycerol and higher fatty acids with the formation of esters. Glycerol in the form of glycerophosphate is formed either from the breakdown product ofcarbohydrates 3 -phospho-glycerol aldehyde, or from glycerophosphate released during the breakdown of triacylglycerols in the cells of tissues. The biosynthesis of fatty acids consists in the gradual elongation of the chain of fatty acid by two carbon atoms until the appearance of a certain fatty acid. This process involves acetyl-CoA, malonyl-CoA, ATP, NADPH 2 , acyl transfer protein and a system of enzymes that are combined into a multi-enzyme complex - fatty acid synthetase (Fig. 10.4). н,с-со-сқ-со-(^) Condensing enzyme Second reductase Acetyl (and acyl) transfer Figure 10.4 - Synthesis of fatty acids Sf co- CHj- CHOH- CH, First reductase НООС-СҚ-С Malonyl transfer 200